<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <link href="https://cdn.bootcss.com/twitter-bootstrap/3.4.1/css/bootstrap.min.css" rel="stylesheet">
    <script src="https://cdn.bootcss.com/jquery/3.3.1/jquery.min.js"></script>
    <script src="https://cdn.bootcss.com/twitter-bootstrap/3.4.1/js/bootstrap.min.js"></script>
</head>
<body>
    <div class="container">
        <div class="row">
            <div class="col-md-8 col-md-offset-2">
                <h1 class="text-center">用户登陆</h1>
                <form action="" method="post">
                    <p>username:
                        <input type="text" name="username" class="form-control">
                    </p>
                    <p>password:
                        <input type="text" name="password" class="form-control">
                    </p>
                    <input type="submit" value="登录" class="btn btn-success btn-block">
                </form>
            </div>
        </div>
    </div>
</body>
</html>